1. Field of the Invention
The present invention relates to a vacuum processing apparatus having a function to remove particles from the surface of a sample stage arranged in a processing chamber disposed in a vacuum processing apparatus in which plasma is generated, and a vacuum processing method using the above-described vacuum processing apparatus. Further, the present invention aims at providing a vacuum processing apparatus capable of applying a cleaning method that removes particles attached to the sample stage easily and with high probability, and a vacuum processing method using the same.
2. Description of the Related Art
In the field of manufacturing semiconductor devices, there are strong demands to improve the yield factor. One of the major causes that deteriorate yield are the particles attached to the sample to be processed, causing pattern defects and creating defective products. There are a number of routes through which particles are attached to the sample to be processed, and especially in apparatuses that process semiconductor devices using plasma, such as sputtering apparatuses, CVD apparatuses or plasma etching apparatuses, the particles existing in the processing chamber become problematic, which are generated from the reaction products of the processing gas and the sample material being processed via plasma treatment, deposited in the processing chamber, and then removed from the chamber wall via pressure variation, contact shock and so on. Furthermore, it is necessary to reduce the amount of particles on the surface of the sample stage, since it is the area that becomes closest to the sample being processed within the processing chamber, and the particles thereon have a high possibility of being attached to the sample to be processed. In recent years, electrostatic chuck force is used widely to support the sample to the stage, but the particles on the surface of the sample stage undesirably widen the distance between the sample and the electrostatic chuck surface, causing attenuation of the electrostatic chuck force.
The sample stage controls the temperature of the sample using both thermal conductance of gas by introducing thermal conductance gas such as helium to the electrostatic chuck surface between the sample and the sample stage and the contact thermal conductance between the sample and the electrostatic chuck surface. However, when the electrostatic chuck force varies by the particles attached to the surface of the sample stage, the thermal conductance efficiency by the contact thermal conductance is deteriorated, and the temperature distribution within the sample becomes uneven. Moreover, when particles are attached to the outer circumference of the sample on the electrostatic chuck surface, thermal conductance gas leak is increased, and the thermal conductance gas pressure between the sample and the electrostatic chuck surface is changed, by which the thermal conductance effect by gas becomes uneven. Thereby, the temperature of the sample stage cannot be controlled to a uniform temperature throughout the whole body of the sample to be processed, and the temperature of the sample becomes unstable and uneven, making it impossible to perform high accuracy processing. Thereby, the reduction of particles on the electrostatic chuck surface of the sample stage is a serious problem to be solved not only from the viewpoint of reducing particles attached to the sample surface but also from the viewpoint of stabilizing and uniformizing the sample temperature.
Generally, particles on the sample stage have been removed by temporarily releasing the interior of the vacuum reactor to atmosphere, wiping off the particles on the sample stage surface directly or replacing the sample stage, and evacuating the interior of the reactor. However, the greatest drawback of such conventional process was that it required a long time before the processing apparatus was restored. Japanese patent application laid-open publication No. 10-321488 (patent document 1) discloses a method for easily removing particles without braking vacuum by placing a dummy sample having an adhesive sheet attached to the rear surface thereof on a sample stage via the same operation as transferring a normal sample, performing electrostatic chuck so as to have particles attach to the adhesive sheet on the rear surface of the dummy sample, and removing the same.
Japanese patent application laid-open publication No. 2005-317782 (patent document 2) discloses a method for removing particles on the rear surface of the sample to be processed by applying high voltage to the sample stage to detach the particles from the stage while introducing dust removal gas so as to remove the particles via shock waves. Furthermore, patent document 2 discloses another method for removing particles on the sample stage by holding the sample up from the sample stage via push-up pins, introducing gas through thermal conductance gas holes, applying high voltage to generate plasma in the space between the sample stage and the sample, and thereby cleaning the sample stage. According to this method, if the particles attached to the sample stage are organic reaction products, for example, the particles can be removed via oxygen- or fluorine-based plasma cleaning.
The adhesive sheet for removing particles is formed of organic polymer, so it may not have sufficient heat resistance. Therefore, if the temperature of the sample stage is high, the adherence property of the of the dummy sample is increased, so that the adhesive agent may remain on the surface of the sample stage during electrostatic chuck, or sample displacement may occur when carrying out the dummy sample. Further, in order to regenerate the used dummy sample, it is necessary to remove the adhesive sheet, clean the sample, and adhere a new adhesive sheet thereto, requiring additional steps to be introduced.
Moreover, according to the method for applying high voltage to the sample stage to detach the particles from the sample stage while introducing dust removal gas to thereby remove particles via shock waves, a large amount of gas is required to remove the particles, and the pressure during gas introduction may cause the substrate to be blown away by the gas.
Further according to the method for generating plasma in the space between the sample stage and the sample to thereby remove particles on the sample stage, in order to remove alumina-based particles, it is necessary to apply a high bias in order to remove the particles via plasma cleaning. Therefore, it is difficult to remove the particles without damaging the sample stage surface. Even if plasma cleaning is performed without applying high bias, the electrostatic chuck surface may be exposed to plasma and damaged thereby. Further, since the sample is simply supported via push-up pins, it is not desirable to raise the gas pressure and increase the gas flow rate, considering the displacement of the sample that may occur. Therefore, the particle removing effect via the hydrodynamic force of gas flow is limited.